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MPI CyberMotionSimulator

The MPI CyberMotion Simulator was developed at the Max Planck Institute for Biological Cybernetics as a novel alternative to traditional motion simulators. It is based on a commercial six-axes serial robot originally designed for use in industries as manipulator. The use of this robot as a motion simulator offers many advantages over standard Stewart platforms with a hexapod motion system, for example higher dexterity, larger motion envelopes, sustained centrifugal accelerations, and the possibility to place subjects in extreme orientations (e.g. upside-down).
 
At the Max Planck Institute for Biological Cybernetics, the robot has been customized for use in basic and applied research by outfitting it with a seat in an enclosed cabin with a curved projection screen. The entire assembly is positioned on a linear track with a range of almost 10 m.
The eight degrees of freedom (axes) of the simulator are not coupled and therefore the motion envelope is extended compared to traditional Stewart platforms. Hence, the simulator can be used to move participants into positions that cannot be attained by a Stewart platform. For example, the enclosed cabin can be positioned above the vertically extended robot arm, such that participants can be rotated along the vertical axis indefinitely and differential thresholds in yaw can be determined. In a different configuration of the simulator, participants can be positioned in any orientation in the enclosed cabin or the seat, even upside-down, to investigate the influence of gravity on perception.
The cabin is equipped with a stereo projection and mounting possibilities for force feedback haptic devices used for flight and driving simulation. The MPI CyberMotion Simulator can be programmed to move participants passively along predefined trajectories. It also allows participants to have complete active control over their movements through the use of various control devices (e.g. steering wheel and pedals). In this mode of operation, the MPI CyberMotion Simulator can be used to simulate the behavior of virtual vehicles such as cars, airplanes, and helicopters.
 
These setup provides visual, auditory and inertial stimuli and  allows to measure physiological parameters, such as eye movements and functional brain imaging (using near-infrared spectroscopy). With these capabilities, several open questions in human vestibular neuroscience (e.g., tilt-translation resolution) and optimized motion cueing algorithms for superior simulator designs can be addressed.

Panoramic Picture inside the CMS cabin

MPI Kukacabin panorama: (C) Ulrich Metz 2011 Schwäbisches Tagblatt GmbH
Cockpitpanorama: Cockpit Regional Jet CRJ700  (C) Chris Witzani 2009 schnurstracks gestaltung und interaktion http://schnurstracks.de/
Aerial panorama: Bourg-en-Bresse vieux quartier (C) Christophe Bouthé 2010 Spheric 360° http://spheric360.fr/

Projection Setup of the CyberMotion Simulator Cabin

The MPI CyberMotion Simulator cabin allows to present visuals to the participant inside the cabin with a large field-of-view (FOV). It consists of two wide angle DLP projectors (eyevis.de) with a resolution of 1920x1200 pixels each. For monoscopic projection the visible FOV is approximately 140° horizontal and 70° vertical. Since there is a large overlap between the projection areas the system can also optionally be used for stereoscopic projection by inserting Infitec interference filters and wearing the corresponding passive stereo glasses.
To correct the image distortions introduced by the curved projection setup we are using real-time warp and blend correction on the graphics card provided by the NVIDIA warp and blend API. The required data for the warping stage is viewpoint-dependent and is generated with a commercial camera-based calibration system (domeprojection.com) which ensures accurate overlap in the projector blend area.
 
We are currently using the following real-time visualization software in the cabin projection setup:

The CyberMotion Simulator and its 8 independent axes

The MPI CyberMotion Simulator with its 8 independent axes
Sustained accelerations are usually simulated by use of motion cueing algorithms that involve washout filters. Using these algorithms, a fraction of the gravity vector generates the sensation of acceleration by an unperceived backward tilt of the cabin. A different solution to simulate sustained accelerations involves centrifugal force. If a subject is rotated continuously, the canal system adapts and the centrifugal force generates the perception of an ongoing acceleration. Both solutions require the subject to be seated in a closed cabin because the visual system would otherwise destroy the illusion.

To achieve continuous rotation around the base axis, the robot arm was modified by the manufacturer (KUKA robot AG, Germany). The robot was equipped with a different transmission and further mechanical modifications. Motor power and electrical control signals are transmitted to the robot by slip rings, an outer slip ring for power lines and an inner slip ring for high frequency signals.
 
In its standard configuration, the cabin is attached to the robot flange from behind. In this configuration the subject faces outwards and it is possible to simulate constant deceleration by rotating the robot around its base axis. The 6 axes of the original robot did not allow the possibility to place the subject facing inwards towards the base of the robot, so as to simulate constant acceleration. In order to achieve this possibility, the cabin was equipped with an actuated seventh axis. The C-shaped axis, along which the cabin can slide, provides the possibility to steer the robot into a position in which the cabin is attached to the robot flange from below. In this configuration, turning the last robot axis allows placing the subject towards the center of rotation that in turn grants the possibility to simulate a constant acceleration or head-centered yaw rotation.
 
The robot is equipped with its 6 axis controller and the 7th axis is equipped with a self developed separate controller. To achieve synchronized operation of the full 7 axis system, a combined control system was developed. This control system also monitors and supervises all safety devices and offers the possibility for manual and automated control of the MPI CyberMotion Simulator.
Last updated: Monday, 11.08.2014